1. Field of the Invention
This invention relates to a shift control apparatus and a shift control method of an automatic speed-change apparatus (transmission) of an automobile for automatically speed-changing a clutch disposed between an engine and the transmission, and for speed-changing a synchromesh mechanism of the transmission which changes a gear mesh mode thereof by an actuator, respectively.
2. Related Art
The above mentioned type automatic transmission is for example disclosed in WO97/05410, and a shift control apparatus thereof is shown in FIG. 8. As apparent from FIG. 8, the shift control apparatus is comprised of a first (select) actuator for operating a clutch 3 disposed between an engine 1 and a speed change apparatus (transmission) 2, a second (shift) actuator 5 for operating each of synchromesh mechanisms in the transmission 2, a power unit 6, a speed-change switch 7 and an electronic control unit (ECU) 8.
The power unit 6 of hydraulic type or electrical type operates the first and second actuators 4 and 5. The speed-change switch 7 is operated by a driver and outputs a speed-change signal corresponding to a target speed-change shift to the ECU 8. The ECU 8, based on the shift-change signal from the speed-change switch 7 and signals from various sensors, commands the power unit 6 to control operation of the first and second actuators 4 and 5 electronically.
Thus, the speed-change signal from the speed-change switch 7 operated (switched) by the driver is processed in the ECU 8, based on which the power unit 6 supplies predetermined operating outputs are supplied from the power unit 6 to the first and second actuators 4 and 5, thereby performing a gear shift so-called xe2x80x9cfinger touch controlxe2x80x9d.
A synchromesh mechanism 9 of the above transmission shown in FIG. 9 is provided with a sleeve 13 and a pair of synchronize rings 16 (briefly called xe2x80x9cringxe2x80x9d hereinafter). The sleeve 13 is mounted, in a gear train including plural gears mounted on an input shaft (speed shaft) 10, a counter shaft 11 and an output shaft 12 disposed parallel to each other, on the counter shaft 11 to be slidable axially and not rotatable relative to the counter shaft 11. Each of the rings 16 frictionally contacts with a cone surface of a gear piece 15 (a clutch gear associated with free-rotate gears 14L and 14H to be rotated integral therewith) so that the sleeve 13 meshes with the gear piece 15 after eliminating a relative rotation difference therebetween.
When a shift of the transmission 2 having the synchromesh mechanism 9 is changed (up-shifted), the ring 16 pushed by the sleeve 13 driven by the second actuator 5, is accelerated by the gear piece 15 of the free-rotate gear 14H which rotates in higher speed than that of the sleeve 13. Accordingly, as shown in FIG. 10, outer tooth 161 of the ring 16 abuts onto a rear surface (lower surface in FIG. 10) 13r of the sleeve 13 facing rearwardly, relative to a rotate direction A (upward in FIG. 10) of the counter shaft 11 (this is called xe2x80x9cbalk pointxe2x80x9d). In a push-apart process after the balk point, the sleeve 13 is as shown by a two-dotted line pushed by an operate force F of the second actuator 5, to push the ring 16 by a drive force F1 leftwardly (in FIG. 10), and to push apart the ring 16 by a push-apart force Fxe2x80x2 downwardly (in FIG. 10). Thus, outer tooth 141 of the gear piece 15 of free-rotate gear 14H rotating in higher rotation speed is pushed apart, so that the sleeve 13 engaged with the gear piece 15 of the free-rotate gear 14H.
On the other hand, when a shift of the transmission 2 having the synchromesh mechanism 9 is down-shifted, the ring 16 pushed by the sleeve 13 driven by the second actuator 5, is decelerated by the gear piece 15 of the free-rotate gear 14L which rotates in lower speed than that of the sleeve 13. Accordingly, as shown in FIG. 11, outer tooth 161 of the ring 16 abuts onto a front surface (upper surface in FIG. 11) 13r of the sleeve 13 facing frontwardly, relative to a rotate direction A (upward in FIG. 10) of the counter shaft 11 (this is called balk point). In a push-apart process after the balk point, the sleeve 13 is as shown by a two-dotted line pushed by an operate force F of the second actuator 5, to push the ring 16 by a drive force F1 rightwardly (in FIG. 11), and to push apart the ring 16 by a push-apart force Fxe2x80x2 upwardly (in FIG. 11). Thus, outer tooth 141 of the gear piece 15 of free-rotate gear 14L rotating in lower rotation speed is pushed apart, so that the sleeve 13 engaged with the gear piece 15 of the free-rotate gear 14L.
The push-apart force Fxe2x80x2 of the ring 16 by the sleeve 13 in shifting-up and shifting-down operations is generally determined by value of a tip angle xcex8 of the chamfer 132 of the sleeve 13 and a value of drive force F of the sleeve 13. Provided that the value of drive force F of the sleeve 13 by the second actuator 5 is constant, the push-apart force Fxe2x80x2 becomes larger as the value of the tip angle xcex8 of the chamfer 132 becomes smaller. However, since the push-apart force Fxe2x80x2 needs to be smaller than the cone torque to perform the synchronize operation, the tip angle xcex8 can not be selected to be smaller over a predetermined value. For this reason, in designing each components, the tip angle xcex8 of the sleeve 13 is determined in advance, then the second actuator 5 which can generate the drive force F sufficient to obtain the force Fxe2x80x2 necessary for push-aparting the ring 16 is selected.
However, in the conventional automatic transmission, there is actually a case where the second actuator 5 which has ability or power twice compared with that required from design aspect is needed. This results from the fact that, when the automatic transmission is installed on the vehicle, the push-apart force Fxe2x80x2 based on the drive force F applied from the second actuator 5 and necessary for the sleeve 13 varies, depending on a resistance of a lubricant oil (briefly called xe2x80x9coilxe2x80x9d hereinafter) contained in a transmission case based on a dynamic viscosity thereof. In detail, in the synchromesh mechanism 9 of the transmission 2 shown in FIG. 9, the dynamic viscosity of oil a surface level of which normally corresponds to position of the counter shaft 11 increases in a low-temperature condition, so that an agitate or stir resistance of the oil also increases. The gear pieces 15 associated with the free-rotate gears 14H and 14L and the rings 16, in rotating in the oil receive the stir resistances Fxe2x80x3 in a direction reverse to the rotate direction A of the counter shaft 11, as shown in FIGS. 10 and 11.
This stir resistance Fxe2x80x3 acts onto the ring 16, especially in the down-shift as shown in FIG. 11, in the direction reverse to the push-apart force Fxe2x80x2 applied to the ring 16 and the gear piece 15 by the sleeve 13. In order to make the push-apart force Fxe2x80x2 larger than the stir resistance Fxe2x80x3 (Fxe2x80x2 greater than Fxe2x80x3), the larger drive force F should be applied to the sleeve 13 from the second actuator 5, which needs to make the power of the second actuator 5 larger. The stir resistance Fxe2x80x3 of the oil increases like an index function as the atmospheric temperature i.e. the oil temperature decreases, and the stir resistance Fxe2x80x3 in the normal temperature may become twice or more when the oil is used in the cold area.
Accordingly, in the conventional automatic transmission, the second actuator 5 shifting the sleeve 13 needs to have the drive force F which can overcome the stir resistance Fxe2x80x3 of the oil due to the dynamic viscosity thereof in the low temperature. As the result, when the second actuator 5 is of hydraulic type operated by an oil pressure or air pressure, diameter of a piston or capacity of an accumulator of pump will becomes larger; when it is of electrical type, necessary current and voltage become larger. Thus, in both cases, the whole shift control system becomes larger, which is inconvenient for the manufacturing cost and the installation. In addition, such drive force F of the second actuator 5 is required only when the vehicle runs in the very cold area where atmospheric temperature is below xe2x88x92(minus) 20xc2x0 C. Making the piston diameter of the actuator and the accumulator of the pump larger for such rare case has little merit and is not practical.
The present invention is made, in view of the above mentioned circumstances of the conventional automatic transmission, and intends to provide a shift control apparatus and a shift control method in the automatic transmission, which can reduce the required value of the drive force for the shift actuator, to make the automatic transmission cheaper and to improve install character thereof.
An inventor of this application has studied hard to overcome the above disadvantage of the conventional automatic transmission, and paid attention the forces applied to the ring 16 and the gear piece 15 from the sleeve 13 and the oil in the push-apart process of the up-shift. In shifting-up operation, as shown in FIG. 10, the free-rotate gear 14H rotates in higher speed than the sleeve 13, the outer tooth 161 of the ring 16 abuts onto the rear surface 13r of the two surfaces of chamfer of the sleeve 13 facing rearwardly relative to the rotate direction A of the counter shaft 11, so that the ring 16 is pushed apart by the push-apart force Fxe2x80x2 of the sleeve 13 directed in the same direction as the agitate resistance force Fxe2x80x3. Accordingly, in the up-shift operation, the push-apart force Fxe2x80x2 can be made smaller depending on value of the agitate force Fxe2x80x3. Thus, the second actuator 5 sufficiently has the smaller force F to push the sleeve 13.
In view of the above, the inventor has hit upon to generate the push-apart force Fxe2x80x2 in the reverse direction to the rotate direction A of the counter shaft 11 and in the same direction as the agitate direction in the down-shift operation as the occasion demands (for example, the vehicle running in the cold area), similar to the up-shift when the vehicle is running in the normal area.
That is, the shift control apparatus of the present invention for controlling an automatic transmission comprises a transmission including a synchro mechanism having at least one set of sleeve and a pair of free-rotate gears relatively rotatable on a rotate shaft; a clutch disposed between said transmission and an engine; a first drive means for operating said clutch; a second drive means for operating the synchro mechanism of said transmission; a third drive means for varying the number of rotation of the engine; and a control unit for controlling said first drive means, said second drive means and said third drive means based on a speed-change signal in a speed-change of said transmission. Said control unit includes a clutch control portion to control said first drive means so that said transmission is separated from the engine, then temporarily connected to the engine and then separated from the engine; a synchro control portion to drive said second drive means so that the synchro mechanism of said transmission is shifted-fall when said transmission is firstly separated from the engine, and is shifted push-in when said transmission is secondary separated from the engine; and an engine control portion to control said third drive means so that the numbers of rotation of the engine is increased when the synchro mechanism is shifted fall and said transmission is temporarily connected with the engine.
The shift control method of the present invention controls an automatic transmission including a transmission having a synchro mechanism having at least one set of sleeve and a pair of free-rotate gears relatively rotatable in a rotate shaft, a clutch disposed between said transmission and an engine, a first drive means for operating the clutch, a second drive means for operating the synchro mechanism of the transmission, and a third drive means for varying the numbers of rotation of the engine, by a control unit having a clutch control portion, a synchro control portion and a engine control portion respectively controlling the first drive means, the second drive means and the third drive means based on a speed-change signal in a speed-change of the transmission. The control method is comprised of steps of a shift-fall step for shifting fall the synchro mechanism by the synchro control portion via the second drive means, in condition where the transmission is separated from the engine by the clutch control portion via the first drive means; a clutch connect step for connecting the clutch temporally by the clutch control portion via the first drive means and for accelerating the engine by the engine control portion via the third drive means, in neutral condition of the clutch performed in said shift-fall step; and a shift push-in step for shifting push-in the synchro mechanism by the synchro control portion via the second drive means, in condition where the transmission is separated from the engine by the clutch control portion via the first drive means.
According to the shift control apparatus and the shift control method of the automatic transmission of the present invention, for example in shifting-down the transmission in which the sleeve is synchronized and meshed with the free-rotate gear rotating in the lower speed than the sleeve when the vehicle is running in the cold area, the rotate speed of the slower free-rotate gear is increased by operation of the clutch and control of opened degree of the accelerator. Thus, the numbers of rotation of the slower free-rotate gear is increased to a level higher than that of the sleeve. In this state, the gear piece of the slower free-rotate gear is synchronized and meshed with sleeve by the drive force of the second drive means. Therefore, in both of the synchronize area and the push-apart area, the ring is hardly reduced in the rotate speed thereof by the free rotate gear, and is brought into condition similar to the up-shift condition. As the result, the direction of force by the sleeve to push apart the ring in the rotate direction and the direction of the agitate resistance applied from the oil to the ring are coincided, so that the necessary drive force for the second actuator to drive the sleeve can be reduced.
The shift control apparatus and the shift control method of the automatic transmission of the present invention can have various embodying modes explained below.
The transmission can include a first type in which an input shaft, an output shaft and a counter shaft are disposed in parallel, or a second type in which the input shaft and the output shaft are disposed on a common axial and the counter shaft is disposed parallel thereto. In the first type, the synchro mechanism can be mounted on the input shaft or the counter shaft; in the second type, it can be mounted on the output shaft or the counter shaft.
The first, second and third drive means can be comprised of a power unit and a first, second and third actuators operated by the power unit. As the actuator, the hydraulic-type actuator using an oil pressure cylinder or an air pressure cylinder, and an electric-type actuator using an electric motor can be adopted. When the actuator is of hydraulic type, the power unit can be comprised of an oil pressure control circuit or an air pressure control circuit; when the actuator is of electric type, the power unit can be comprised of a power amplify circuit using a semi-conductor. The control unit can be comprised of an electronic control unit (ECU).
The synchro control portion can shift-fall the synchro mechanism, after the first interruption of the clutch is detected by sensors to detect decrease of the numbers of rotation of the engine or the input shaft, or decrease of a vehicle running speed. The synchro control portion, when temperature decrease of an oil in the transmission below a predetermined value is detected by sensors such as an oil temperature provided in the transmission a water temperature provided in the engine 1 or by an input rotation in the neutral condition, can cause a sleeve to separate from a faster free-rotate gear in a shift-fall of the synchro mechanism and the sleeve to engage with a slower free-rotate gear in shift push-in of the synchro mechanism.
The clutch control portion can temporarily connect the clutch, after the shift-fall of the synchro mechanism is detected by a stroke sensor disposed in the second drive means. The engine control portion, after the temporal connection of the clutch is detected, can accelerate the engine so that the numbers of rotation of the slower free-rotate gear exceeds the numbers of rotation of the sleeve of the synchro mechanism.
The temporally connected time period of the clutch by the clutch control portion and accelerated time period of the engine by the engine control portion, can be controlled by a timer operating in a predetermined time period after the shift-fall of the synchro mechanism by the synchro control portion. Also, the temporally connected time period of the clutch by the clutch control portion and accelerated time period of the engine by the engine control portion, can terminate when the numbers of rotation of the slower free-rotate gear exceeds the numbers of rotation of the sleeve of the synchro mechanism.